1. Field of the Invention
The present invention relates to an AV communication control circuit and an AV communication control program for transmitting or receiving AV data while realizing the copyright protection.
2. Description of the Related Art
The products called digital information home electronics are becoming popular. These products are expected to become even more popular in conjunction with the start of the digital broadcasting, and include all kinds of products for handling digital data and digital contents such as digital broadcasting compatible TV, set-top box, digital VTR, DVD player, hard disk recorder, etc.
The quality of the digital data and digital contents will not be degraded even when they are copied, and the copies can be made easily, so that there is a need to provide a measure for the copyright protection in advance. For example, in the IEEE 1394 which is a digital network for connecting digital AV devices, the authentication and key exchange mechanism and the data encryption function are provided.
Here, consider a case of transferring the AV data that requires the copyright protection, from some transmission device. What needs to be taken into consideration here is that the copyright protection presupposes to allow the exchange of the AV data within a range of personal (or family) entertainment, but to prevent the exchange of the AV data with a third person (unless the permission from the copyright holder is given).
Usually, the exchange of data with a third person is carried out through a public network such as the Internet, and the exchange of data inside the home or the personal exchange of data is carried out on a closed home network such as the IEEE 1394 or a radio network.
The IEEE 1394 is a representative digital network for connecting digital AV devices, and provided with the authentication and key exchange mechanism and the data encryption function. This mechanism is called DTCP (Digital Transmission Control Protection) (see documents disclosed at “http://www.dtla.com”, for example). Basically, the DTCP encryption and the authentication and key exchange mechanism are provided inside an LSI of the IEEE 1394, and it is often provided with a mechanism for encrypting the AV data immediately before transmitting them to the IEEE 1394, and decrypting them immediately after receiving them, in the case of transmitting/receiving AV data to be protected through the IEEE 1394 (see Japanese Patent Application Laid Open No. 2001-308775).
What is likely to attract attentions in near future is the home radio LAN. The IEEE 802.11 standard which is one of the radio LAN standards is rapidly spreading to offices/homes, and it is highly likely to carry out the exchange of the AV data that require the protection on the radio LAN in near future.
Even in this type of the radio LAN, there is a need to consider the copyright protection mechanism, and such a mechanism will most likely be incorporated in an LSI of the radio LAN, in view of the past experience of the IEEE 1394.
However, the known radio LAN has been basically targeting a PC network. The radio LAN interface in the PC (interface between a CPU of the PC and the radio LAN) is provided through a general purpose bus such as PCI bus, and for this reason, the integrated circuit of the radio LAN often has a PCI bus interface.
On the other hand, in near future, it is highly likely that the radio LAN is implemented on the so called AV devices such as TV, DVD, etc. An interface between an AV processing unit (such as AV decoder) and a network in these AV devices is in general an interface for directly exchanging AV stream data, for various reasons such as securing the synchronization. Thus the integrated circuit of the radio LAN should preferably have this AV stream interface, Also, the implementation of the copyright protection function is indispensable.
However, when the copyright protection function is provided inside the integrated circuit of the radio LAN, the AV data to be inputted/outputted to/from the integrated circuit of the radio LAN have to be non-encrypted raw data, and this implies that the raw data will flow through the general purpose bus such as PCI bus. In the general PC, it is relatively easy to produce a program for storing data on the general purpose bus into a specific region, so that the allowing the raw AV data to flow through the general purpose bus is problematic.